The present invention relates to new derivatives of the compound XK-88-5 and a process for the production thereof.
XK-88-5 is one factor of a series of related antibiotic compounds, XK-88 series of antibiotics, produced by culturing a microorganism belonging to the genus Streptomyces. XK-88-5 and the fermentative production thereof are disclosed in U.S. Pat. No. 3,939,043 issued Feb. 17, 1977. The XK-88 series of antibiotics are also known as seldomycins. XK-88-5 (seldomycin factor-5) exhibits a high antibacterial activity. New semisynthetic derivatives of XK-88-5 would, therefore, be useful as antibacterial agents. However, since XK-88-5 represented by the formula: ##STR2## has six primary amino groups in the molecule, it is difficult to introduce a substituent into a specific amino group in order to prepare new derivatives. Therefore, it is very desirable to provide a method of protecting a particular amino group in the molecule of XK-88-5 and to provide a derivative of XK-88-5 having a protected amino group at a particular position.
It is well known that when an aminoglycoside antibiotic is reacted with an amino-protecting reagent, the amino group at the 6'-position is readily protected with the amino-protecting group.
It has been found that, when XK-88-5 is reacted with an urethane-type amino-protecting reagent, the amino group at the 2"-position of XK-88-5 is selectively formylated. In that case the amino group at the 6'-position may be simultaneously protected or not protected.
As a conventional method of formylating an amino group, a method using ethyl formate or a mixture of formic acid and acetic anhydride is known. The known method is described in "Protective Groups in Organic Chemistry" pages 46-49, (Plenum Press, 1973). According to the known method, most of the amino groups are formylated and it is impossible to formylate a particular amino group of XK-88-5 selectively. For example, Japanese Unexamined Patent Publication No. 35129/75 discloses a method in which an aminoglycoside antibiotic having a deoxystreptamine ring is reacted with a mixture of formic acid and acetic anhydride or with active esters of formic acid such as p-nitrophenylformate, and all amino groups of the antibiotic are formylated.